Lighting peg with variable pulsation rate

ABSTRACT

In a lighting peg with a variable pulsation rate including a square outer casing provided with a solar cell and a battery and adapted to be installed at an intersection of two roads, light emitting diodes and a photoelectric conversion element are provided on each side surface of the square outer casing. An ambient light sensor for detecting ambient light and a pulse signal generating circuit for generating pulse signals are further provided together with vehicle sensors, each including the photoelectric conversion element, a differential circuit and a comparator. A control circuit including OR gates for receiving the outputs of the vehicle sensors, discriminating circuits for discriminating the outputs of the OR gates and pulsation rate control circuits for controlling the rate of pulsation are further provided in the lighting peg so that, when a vehicle approaches the road intersection along a first road is detected by one of the vehicle sensors, the rate of pulsation of light emitted from the light-emitting diodes into the second road is varied in a predetermined manner.

BACKGROUND OF THE INVENTION

This invention relates to a variable frequency lighting peg adapted tobe installed at the center of road intersections, and constructed sothat when a vehicle is approaching the intersection along one of theroads, the rate of pulsation of light emitted from the peg to anotherroad can be varied for warning the driver of a car coming along thesecond road to exercise caution with respect to the approaching vehicleon the first road.

Various lighting pegs have been heretofore proposed.

For instance, Japanese Utility Model Laid-Open Publication No.152013/1986 discloses a road-surface mounted type of signaling devicecomprising a solar cell, battery, and a light-emitting diode, and thatdetermines the light intensity of the surrounding area, and that isautomatically operate so that the light pulsates throughout the night.Also, in an automatic flashing lamp indicating the edge (or shoulder) ofa road, a first photoelectric conversion element senses the ambientlight, while a second photoelectric conversion element senses light froma vehicle so that the lamp operates to pulsate (refer to JapaneseUtility Model Publication No. 39915/1977). Otherwise proposed is aself-lighting type of road marking device wherein ambient light isdetected from the output voltage of a solar cell, while light from avehicle is sensed by a photoelectric conversion element, and a lightemitting diode is thereby operated so as to pulsate (for instance referto Japanese Utility Model Laid-Open Publication No. 68113/1986).

As a result of recent traffic clogging in the majority of principalroads, back roads of narrower widths tend to be utilized as detours.Ordinarily, the provision of regular traffic signals is not sufficientin these back roads, and therefore lighting pegs and the like of theautomatic flashing type are frequently used to supplement the trafficsignals. However, since there is a limitation in the capability of suchauxiliary devices, the number of traffic accidents occurring in the backroads is constantly increasing and a counter measure to this problem hasbeen urgently required.

Among the aforementioned conventional techniques, a lighting peg thatoperates to pulsate throughout the night is adapted to indicate thepresence of an intersection of roads, and to warn drivers of vehiclesand pedestrians to exercise caution. However, the reason for most of theintersection accidents is in the disobeyance of temporary stopping rulesand carelessness of drivers of vehicle coming along the other road fromeither the right or left directions. Therefore simply indicating thepresence of an intersection is not sufficient to preventing suchaccidents.

In another of the conventional techniques where the peg pulsates onlywhile a vehicle approaches the intersection, the presence of theintersection is not indicated to pedestrians or the riders of bicycles.Furthermore, when a vehicle comes along a first road of an intersection,and thereafter another vehicle approaches the intersection along anotherroad, the approach of the second vehicle is not informed to the driverof the first-mentioned vehicle, and therefore such a technique cannot beconsidered to be satisfactory.

SUMMARY OF THE INVENTION

A primary object of this invention is to provide a lighting peg with avariable pulsation rate capable of overcoming the above describeddifficulties of the conventional devices.

Another object of the invention is to provide a lighting peg with avariable pulsation rate capable of indicating an intersection of tworoads at night time by emitting light pulses of a predeterminedpulsation rate.

Still another object of the invention is to provide a lighting peg witha variable pulsation rate wherein the rate of pulsation of the lightemitted toward one road can be increased to two or four times greaterthan the predetermined pulsation rate according to the condition ofvehicles incoming along the other road.

These and other objects of the present invention can be achieved by alighting peg with a variable pulsation rate comprising a square outercasing provided with a solar cell and a battery, and adapted to beinstalled at an intersection of two roads; light-emitting diodes and aphotoelectric conversion element provided on each side surface of theouter casing; an ambient light sensor comparing the output voltage ofthe solar cells with a reference voltage; a pulse signal generatingcircuit operated by the output of said ambient light sensor so as togenerate a number of pulse signals of different frequencies; uponoperation of the pulse signal generating circuit, the light-emittingdiodes provided on all of the side surfaces being operated by one of thepulse signals having a lowest pulsation rate; vehicle sensors eachcomprising the afore-mentioned photoelectric conversion element seriesconnected with a variable resistor, a differential circuit connectedacross said variable resistor, and a comparator comparing the output ofthe differential circuit with a reference voltage; and a control circuitcomprising OR gates each receiving the output of an opposite pair of thevehicle sensors, discriminating circuits discriminating the outputs ofthe OR gates, and the rate of pulsation control circuits which controlthe rate of pulsation of light emitted from the light-emitting diodestoward the intersecting roads in accordance with those of the pulsesignals generated from the pulse signal generating circuit.

More specifically, when the output of the ambient light sensor isbrought to the high level in the evening, the pulse signal generatingcircuit is operated to generate a number of pulse signals of differentrates, and in the case where a vehicle approaches the intersection fromeither of two directions along a first road, rate of pulsation of thelight emitted from the peg in the opposite two directions along a secondroad is increased to, for instance, a value twice as large as the rateof pulsation of the light ordinarily emitted from the peg at night.

At this time, should another vehicle approaches the intersection alongthe second road before the vehicle in the first road passes through theintersection, the rate of pulsation of the light emitted from thelighting peg in two directions along the first road is also increased toa value twice as large, while the rate of pulsation of the light emittedfrom the peg in two directions along the second road is increased to,for instance, four times as large as what it is ordinarily.

When the vehicle in the first road thereafter passes through theintersection, the rate of pulsation of the light emitted along thesecond road is reduced to the ordinary value.

In addition, since each of the aforementioned vehicle sensors includes adifferential circuit connected to the output of the photoelectricconversion element, the sensor can detect only varying rates of light,thereby substantially eliminating erroneous operation caused by theambient light.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a perspective view showing a preferred embodiment of thepresent invention;

FIG. 2 is an elevational view, partly in section, of the embodimentshown in FIG. 1; and

FIG. 3 is a diagram showing an electric circuit used in the embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of this invention will now be described withreference to the accompanying drawings.

A lighting peg constituting the embodiment comprises an outer casing 1of a square shape having four side surfaces as shown in FIGS. 1 and 2. Asolar cell 2 is provided on an upper surface of the outer casing 1 whilea number of phototransistors 4 operable as photoelectric conversionelements and a light-emitting diode 3 are provided on each of the fourside surfaces of the outer casing 1. The solar cell 2, light-emittingdiodes 3, phototransistors 4, and the battery 6 are connected to form anelectric circuit 5 which is also installed in the casing 1.

FIG. 3 illustrates the electric circuit 5 which comprises vehicle sensorA₁, A₂, A₃ and A₄ for sensing the light of vehicles approaching theintersection from four directions (A), (B), (C) and (D) along the tworoads, an ambient light sensor B for sensing light of the surroundingarea, a pulse signal generating circuit C, light-emitting diode groupsE₁, E₂, E₃ and E₄, and a control circuit D for controlling thelight-emitting diode groups through energizing circuits 35 and 36 on thebasis of the signals output from the vehicle sensors A₁, A₂, A₃ and A₄which receive the light of vehicles approaching the intersection fromthe four directions of (A), (B), (C) and (D) as shown in FIG. 1.

The ambient light sensor B is constructed so that the output voltage ofsolar cell 2 is divided by variable resistor 7 into a voltage having amaximum value of V_(DD) -1 V, and a comparator 9 made of an operationalamplifier compares the thus divided voltage with a reference voltage setby another variable resistor 8. The comparator 9 delivers an output ofhigh level when the voltage at a point b is higher than the voltage at apoint a, and conversely when the voltage at the point b is lower thanthe voltage of the point a, and the output of the comparator 9 becomeslow level.

Each of the vehicle sensors A₁, A₂, A₃ and A₄ includes a phototransistor4 connected in series with a variable resistor 11. The variable resistor11 is adjusted beforehand so that in the evening, the voltage obtainedat a point c is made equal to V_(DD) -1 V. A differential circuitcomprising a capacitor 10 and a resistor 15 is connected to thesubsequent stage, so that the variation of the voltage at the point isdelivered from a point d. That is, when the voltage at the point crises, the voltage of the point d rises in accordance with the voltagevariation at the point c, and when the voltage at the point c is notvaried, the voltage of the point d goes back to zero volts after a timeperiod determined by the time constant of the differential circuit. Whenthe voltage of the point c falls, the voltage of the point d becomes anegative value. However, by the effect of a diode 14 connected in areverse polarity between the point d and the earth, the voltage of thepoint d goes back to zero volts within a short time. A comparator 13compares the output of the differential circuit with a reference voltageset by a variable resistor 12, and when the output of the differentialcircuit is higher than the reference voltage, the output of thecomparator 13 is made high level, but when the output of thedifferential circuit is lower than the reference voltage, the output ofthe comparator 13 is made low level.

The pulse generating circuit C comprises an oscillator 37, an octonarycounter 30, OR gates 31 and 32, and an inverter. When the output of thecomparator 9 of the ambient light sensor B is at the high level, theoscillator 37 oscillates at a duty cycle having a duration timesufficient for lighting the light-emitting diodes. At the same time, thereset input of the octonary counter 30 becomes low level, so that thecounter 30 starts to operate so as to sequentially deliver pulse signalsQ0 to Q7. As a consequence a pulse signal of a longest repetition periodis delivered from a point U, while another pulse signal one half of thatof the first-mentioned pulse signal is delivered from the point V due tothe presence of an OR gate 32, and still another pulse signal having arate 1/4 that of the same pulse signal, is delivered from the point Wdue to the presence of another OR gate 31.

The control circuit D comprises discriminating circuits 18, 19,pulsation rate control circuits 20, 21, two OR gates 16, 17 and two ANDgates 33, 34. When either one or both of the vehicle sensors A₁ and A₃deliver an output or outputs of high level, the output of the OR gate 16becomes high level. Likewise, when either one or both of the vehiclesensors A₂ and A₄ deliver an output or outputs of high level, the outputof the OR gate 17 becomes high level. According to the variation oflevels of the output points j and k of the OR gates 16, 17, thediscriminating circuit 18 delivers outputs as shown in Table 1 from thepoints l and m. In a similar manner, according to the variation oflevels of the same output points j and k of the OR gates 16, 17, thediscriminating circuit 19 delivers outputs as shown in Table 2 from thepoints m and n.

                  TABLE 1                                                         ______________________________________                                        (H: high level, L: low level)                                                        Variation of levels                                                    ______________________________________                                        input j      L     H    H    L    L    L   H    H   L                               k      L     L    H    H    L    H   H    L   L                         output                                                                              l      L     L    L    H    L    H   H    L   L                               m      L     L    H    L    L    L   H    L   L                         ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        (H: high level, L: low level)                                                        Variation of levels                                                    ______________________________________                                        input j      L     H    H    L    L    L   H    H   L                               k      L     L    H    H    L    H   H    L   L                         output                                                                              m      L     L    H    L    L    L   H    L   L                               n      L     H    H    L    L    L   L    H   L                         ______________________________________                                    

The pulsation rate control circuit 20 is so constructed that when thelevels of the points l and m are both low level, only a point o amongthree points o, p and q of the circuit 20 becomes high level, and wheneither one of the points l and m is at high level, only the point pamong the points o, p and q becomes high level, and likewise, when boththe points l and m are high level, only the point q among the threepoints o, p and q becomes high level. When the point o becomes highlevel, a pulse signal having a longest repetition period is deliveredfrom an OR gate 28 of the pulsation rate control circuit 20. Likewise,when the point p becomes high level, a pulse signal having a repetitionperiod of one half that of the longest, is delivered from the OR gate28, and when the point g becomes high level, a pulse signal having arepetition period of 1/4 that of the longest is delivered from the ORgate 28.

The pulsation rate control circuit 21 is also constructed so that therate (or repetition period) of the output signal is controlled in asimilar manner by the levels of the points m and n.

The AND gate 33 provided subsequent to the OR gate delivers a high leveloutput when the outputs of the oscillator 37 and the OR gate 28 are bothhigh level, and the AND gate 34 provided subsequent to the OR gatedelivers an output of high level when the outputs of the oscillator 37and the OR gate 29 are both at a high level.

The above described embodiment of this invention operates as follows,when the power source is applied in the day time, the output voltage ofthe solar cell provided in the ambient light sensor B becomes high, anda voltage divided from the output voltage rises to exceed of thereference voltage. Thus, the output of the comparator 9 becomes lowlevel, so that the oscillator 37 in the pulse signal generating circuitC does not operate. At this time, the reset input of the octonarycounter 30 becomes high level, and therefore the outputs from the u, vand w points of the counter are all brought to low level. As aconsequence, the outputs of the AND gates 22, 23, 24, 25, 26 and 27 areall brought to the low level as well as the outputs of the OR gates 28and 29 and the AND gates 33 and 34, so that the output of thelight-emitting diode energizing circuits 35 and 36 are held at the lowlevel and the light emitting diodes groups E₂, E₁, E₄ and E₃ are thusheld in the OFF state. Furthermore, in the daytime, the voltages at thepoint c in the vehicle sensors A₁, A₂, A₃ and A₄ are not varied, so thatthe voltages at the point d is held lower then the reference voltage andthe output of the comparators 13 are consequently brought down to thelow level.

In the evening when it becomes dark, the output voltage of the solarcell in the ambient light sensor B is reduced. When the voltage at apoint a is reduced to lower than the reference voltage at a point b, theoutput of the comparator 9 becomes high level. As a result, theoscillator 37 starts to operate, and since the reset input of theoctonary counter 30 becomes low level, pulse signals of three differentrates are obtained at the points u, v and w. At this time, the voltagesof the point c in the vehicle sensors A₁, A₂, A₃ and A₄ are alsoreduced. However, the voltages at the point d are held at lower than thereference voltages at a point e, so that the outputs of the comparators13 obtained at points f, g, h and i are held at a low level as well asthe outputs obtained at points j and k from the OR gates 16 and 17. As aconsequence, the voltages at the points l, m, n are brought to the lowlevel as shown in the Tables 1 and 2, and only the voltages at points oand r are brought to the high level. Thus, the pulse signal of thelongest period is delivered from the OR gates 28 and 29, and the outputsignals thus delivered are applied through the AND gates 33 and 34 tothe energizing circuits 35 and 36, so that the light-emitting diodegroups E₂, E₁, E₄ and E₃ are operated in accordance with the pulsesignal of the longest period.

In the case where a vehicle or vehicles approach the intersection from(A) or (C) or both directions along a first road, a current flowsthrough the phototransistor 4 in the corresponding sensors, therebyincreasing the voltage of the point c, and therefore the voltage of thepoint d. When the voltage of the point d rises to exceed the referencevoltage, the output of the comparator 13 in the corresponding sensor orsensors becomes high level together with the output of the OR gate 16.In this case, the point j becomes high level, leaving the point k at lowlevel, so that the point l becomes high level while the point is left atlow level. As a result, the point o becomes high level causing the ANDgate 22 to deliver the pulse signal of longest period, the output of theAND gate 22 is sent through the OR gate 28 and the AND gate 33 to thediode energizing circuit 35, so that the light-emitting diode groups E₂and E₄ are operated by the pulse signal of the longest period. On theother hand, the point m becomes low level and the point n becomes highlevel, thereby bringing the point s to high level, so that a pulsesignal that is 1/2 of the longest period is delivered from the AND gate26, and the device energizing circuit 36 operates the light-emittingdiode groups E₁ and E₃ directed to the second road at a pulsation ratetwice as large as that of the initial pulsation rate of the longestperiod.

When a vehicle running along the first road in (A) or (C) directionpasses through the intersection, thereby reducing the light received bythe vehicle sensor A₁ or A₃ or both of them, the voltage at the point din the sensor is reduced. When the voltage of the point d is reduced toa value lower than the reference voltage, the output of the comparator13 becomes low level. Thus, the output of the points j and k are bothbrought to the low level, so that the points l, m and n are all broughtto the low level. As a result, the points o and p becomes high level,and the pulse signals of the longest period are delivered from the ANDgates 22 and 25. The pulse signals are then passed through OR gates 28and 29 and AND gates 33 and 34 to the light-emitting diode energizingcircuits 35 and 36, so that all of the light-emitting diode groups E₂,E₁, E₄ and E₃ re operated at the longest period (lowest rate).

Likewise, when a vehicle approaches the intersection from (B) or (D) orboth directions along a second road, the point j is held at low levelwhile the point k is brought to the high level. Thus, point l becomeshigh level while the point m becomes low level, and since the point p isbrought into high level, a pulse signal of 1/2 the repetition period (arate twice as fast) is delivered from the AND gate 23, and operates thelight-emitting diode energizing circuit 35 through OR gate 28 and ANDgate 33, so that the light-emitting diode groups E₂ and E₄ directed tothe first road are lit at a rate twice as fast. At the same time, thepoints m and n are brought into low level while the point is held athigh level. As a consequence, a pulse signal of the slowest rate isdelivered from the AND gate 25 to the diode energizing circuit 36through OR gate 26 and AND gate 34, so that the light-emitting diodegroups E₁ and E₃ are operated at the slowest rate. When the vehiclealong the second road passes through the intersection, and the lightreceived by the corresponding vehicle sensor is reduced, the voltage atthe point d is reduced. The output of the comparator 13 of the sensor istherefore reduced to low level together with the output of OR gate 17.As a consequence, the points j and k are both brought to the low level,and all of the light-emitting diode groups E₂, E₁, E₄ and E₃ areoperated at the slowest rate (or initial rate).

As described before, when a vehicle approaching the intersection from(A) or (C) direction or from both of the (A) and (C) directions aredetected by the sensor or sensors, the point j becomes high level, whilethe point k becomes low level, thereby bringing the points 1 and intolow level, and the point into high level. At this time, the point obecomes high level thereby lighting the diode groups E₂ and E₄ at theinitial slow rate, while the point s becomes high level thereby lightingdiode groups E₁ and E₃ at a rate twice as fast as the initial rate.

At the time of the above described operation, when a vehicle coming tothe intersection from (B) or (D) direction or both are detected by thecorresponding vehicle sensor the point k on the output side of the ORgate 17 becomes high level. Thus the point l becomes low level, whilethe point m becomes high level, and since the point among the points o,p, and q is brought to a high level, a pulse signal of 1/2 of thelongest period is delivered from the AND gate 23. Accordingly, thelight-emitting diode groups E₂ and E₄ are operated at a rate twice asfast as the initial rate. At this time, since the point n is also heldat high level, the point t among the points r, s and t becomes highlevel, so that a pulse signal of 1/4 the repetition period (a rate fourtimes as fast) is delivered from the AND gate 27, and the light-emittingdiode groups E₁ and E₃ are operated at a rate four times as fast as theinitial rate. When the vehicle approaching the intersection from (A) or(C) direction or both of these directions has passed through theintersections, the output point j as the OR gate 16 comes low level, sothat the point l becomes high level, while the points m and n become lowlevel. At this time, the point p among the points o, p and q becomeshigh level, and therefor a pulse signal of one half the period (a ratetwice as fast) of that of the initial signal is delivered from the ANDgate 23, and the light-emitting diode groups E₂ and E₄ are operated atthe rate twice as fast. Furthermore, since the point r among the pointsr, s and t, becomes high level, the AND gate 25 delivers a pulse signalof the longest period, and therefore the light-emitting diode groups E₁and E₃ are operated at the initial rate.

When the vehicles running along the (B) or (D) direction or both of thedirections also have passed through the intersection, the outputs fromthe sensors A₁, A₂, A₃ and A₄ become low level, and the voltages of theoutput points j and k of the OR gates 16, 17 are thereby brought to thelow level. Thus only the point among the points o, p and q becomes highlevel, and also only the point r among the points r, s and t becomeshigh level. As a consequence, the output pulse signal of longest periodis delivered from both of the AND gates 22 and 25, and thelight-emitting diode groups E₂, E₁, E₄ and E₃ are all operated at theinitial rate.

Although the cases where the vehicles approach the intersection firstlyfrom (A)-(C) directions and then from (B)-(C) directions have beendescribed above, it is apparent that operations of the diode groups aresimilar to the above described cases regardless of the case where thevehicles approach the intersection firstly from (B)-(D) directions andthen (A)-(C) directions, except that the sequences of varying rates ofthe operation of the diode groups are reversed.

In the morning when the ambient light gradually increases, the lightquantities received by the phototransistors 4 in the sensors A₁, A₂, A₃and A₄ also increase, and the voltage at the point c in each sensorrises. However, the rate of increase of the voltage of the point c isextremely slow, and hence the voltage of the point d is held at nearlyzero volts, which is far lower than the reference voltage at the pointe, so that the output of the comparator 13 is held at a low level, andthe light-emitting diode groups E₂, E₁, E₄ and E₃ are operated at theinitial rate. However, when the output voltage at the point a of thesolar cell 2 becomes higher than the reference voltage at the point b,the output of the comparator 9 becomes low level thereby terminating theoperation of the oscillator 37. Furthermore, the reset input of theoctonary counter 30 becomes high level, so that the outputs as thepoints u, v and w are all brought into low level, thereby turning offthe light emitting diode groups E₂, E₁, E₄ and E₃.

According to the lighting peg of the present invention, while theall-night flashing capability of the conventional device is maintained,the rate of pulsation of the light along one road is varied to 1/2 or1/4 of the initial value when a vehicle approaches the intersectionalong the other road, so that not only the presence of the intersectionis informed to the drivers of vehicles or pedestrians, a warning that avehicle is approaching the intersection along the other road can beissued at the appropriate time, and the occurrence of collisionaccidents at the intersections having no traffic signals can beprevented.

What is claimed is:
 1. A lighting peg with a variable pulsation rate,comprising:a square outer casing provided with a solar cell and abattery, and adapted to be installed at a road intersection;light-emitting diodes and a photoelectric conversion element provided oneach side-surface of said outer casing; an ambient light sensor forsensing light of a surrounding area; a comparator for comparing anoutput voltage of said solar cell with a reference voltage and providingan output; a pulse signal generating circuit operated by an output ofsaid ambient light sensor so as to generate a number of pulse signals ofdifferent rates; wherein upon operation of said pulse signal generatingcircuit, said light-emitting diodes provided on all of the side surfacesbeing operated by one of said pulse signals having the lowest rate;vehicle sensors on each of said sides of said casing, each comprisingsaid photoelectric conversion element series connected with a variableresistor, a differential circuit connected across said variableresistor, and a comparator comparing an output of said differentialcircuit with a reference voltage; and a control circuit comprising ORgates, each receiving outputs of a pair of the vehicle sensors onopposite sides of said casing, discriminating circuits discriminatingthe outputs of the OR gates, and pulsation rate control circuits whichcontrol the rate of pulsation of the light emitted from said lightemitting diodes toward said road intersection in accordance with thoseof the pulse signals generated from said pulse signal generatingcircuit.
 2. The lighting peg with a variable pulsation rate according toclaim 1 wherein said pulse generating circuit includes an octonarycounter provided in combination with two OR gates and an inverter, sothat three pulse signals having a slowest rate and twice and four timeslarger than the slowest rate are delivered from said signal generatingcircuit.
 3. The lighting peg with a variable pulsation rate according toclaim 2 wherein said discriminating circuits in combination deliverthree outputs simultaneously, the conditions of which are varied inaccordance with the outputs of said OR gates each receiving the outputsof a pair of said vehicle sensors sensing light of vehicles approachingthe intersection from two opposite directions of one road.
 4. Thelighting peg with a variable pulsation rate according to claim 3 whereineach of said pulsation rate control circuits is made operable so thatdepending on the conditions of two of the three outputs delivered fromsaid discriminating circuits, only one of three control lines in thepulsation rate control circuit is brought to a high level, wherebyeither one of said three pulse signals of different rates generates insaid pulse signal generating circuit is delivered from said pulsationrate control circuit.